I watched the show a number of times in the earliest weeks and just came back to it recently. While I haven't personally caught an uncomfortable length of vamping, several of my friends have seen them in the more recent shows, which to me would seem to indicate the lack of participation. When the show was new, games were just zipping along.
While I agree with Mark that it's ideal to let the viewers hang and pile on entries, I don't think it's always the case. For example, the times where they make no mistake this is what they're doing. For instance, when Mel offers a "clue" to the answer(s) they want, they'll take a noticeable pause, despite what was earlier a steady stream of callers. Or when they offer a bonus to the next caller - such as "double money for the next caller" or "two guesses for the next two callers" - they will always let the offer stay up for a while. This is obviously so Joe Sixpack thinks he can swoop in and take whatever money there is on offer. They've recently taken to having commercials midgame, even after giving away a hint. As if the pause wasn't enough of a hint, after said pause is over, the "Lounge" doesn't include its normal verifying prompt, instead jumping to the names immediately.
Quick aside to those who have been on - what exactly happens when you get the call and summarily go on the show? I've been on radio call in shows before, so I think it's similar, but I'm interested to hear it from PlayMania contestants specifically.
-Jason